1. Field of the Invention
This invention relates to an insecticide dispenser used indoors for extermination of insects such as cockroaches, flies and mosquitoes. The dispenser uses a fan to disperse the insecticide, shutters to open and close an inlet and an outlet of the dispenser, and a controller to command the operation of the shutters and to drive the fan. Such a dispenser is used in restaurants, kitchens, as well as in ordinary households, buildings in general and sports facilities.
2. Description of Related Art
Generally, harmful insects such as cockroaches, flies and mosquitoes infest human habitations. Extermination of these harmful insects is essential to public hygiene and to business performance, and is done as a regular practice not only at restaurants, in accordance with sanitary regulations, but also in households, offices, and sports facilities such as indoor pools.
One method employed to exterminate these harmful insects is a room insecticide dispenser which disperses vaporized insecticide. The dispenser employs an electric fan to take in air and spread the insecticide into the room. A timer is installed in the dispenser such that the action of the fan is controlled by the timer, and the insecticide may be dispersed when no one is around, i.e. at night. This avoids the potential threat to humans by the insecticide dispersion. Moreover, by using a timer, the fan can be turned on and off at fixed intervals thereby preventing regeneration or reinhabitation of insects from the outside.
The insecticide used in the dispenser must be easily volatilized in the dispenser and suitable for blending with the air. Therefore, the insecticide should have a high vapor pressure and volatilize continuously at room temperature. In general, solid or liquid insecticides which are easy to handle and which last a long time are used.
Such dispensers comprise a container having an inlet through which room air is drawn and an outlet through which the mixture of insecticide and room air is expelled from the container. Since the insecticide is easily volatilized, it may be inadvertently expelled if the inlet and the outlet remain open during a time when the dispenser is not in use. This is especially true if the insecticide is odorless, since the dispersion of the insecticide cannot be detected. It is not desirable for the insecticide to be carelessly dispersed. U.S. Pat. No. 5,335,446 issued Aug. 9, 1994 addresses this problem. The '446 patent teaches that both the inlet and the outlet have shutters and that the opening and closing of the shutters are linked to the operation of the fan. By using a timer and linking the opening and closing of the inlet and outlet with the fan, the starting and ending of the dispersion action of the dispenser is controlled. Namely, the dispenser disperses the insecticide by driving the fan at a set start time and, after the dispersion, the fan stops at a set end time, both of which are preset in the timer. As it operates according to this program, manual operation is not necessary. A motor is used to open and to close the shutters at the dispersion start time and at the dispersion end time, respectively.
There are, however, some problems with the dispenser taught in the '446 patent. If the shutters of the dispenser are opened and a problem occurs with the power source, such as a power outage, disconnection of the electric cord, or a great drop in power source voltage, then the shutters remain in the open position. This results in the vaporized insecticide escaping and may result in a higher concentration of the insecticide in the room than is necessary. It is not only a waste of the insecticide, but can also cause a potential but unperceived threat to persons in the room. Further, since the timer only has the capability of a single start and stop time, it is necessary to re-set the start time in the timer when the dispersion action start time is changed. Therefore having different start times on different days is troublesome.
Additionally, once the dispersion start and end times are set in the timer, even if the dispersion is not desired on a given day, the insecticide is dispersed at the set start time, except in the case where the set time is canceled or the power source is "off".
Furthermore, since there is no tester which checks to insure that the dispenser has stopped at the preset end time, it is necessary to test the operation by means of first setting the times and then returning to manually check and insure that the dispersion action of the dispenser has stopped.
Furthermore, since the power is provided to the dispenser by means of a power source switch, if the switch fails for any reason, then the dispensing of the insecticide is not accurately controlled.
Furthermore, installed in the dispenser is a heater which acts at a low temperature, for example, under 20.degree. C., to vaporize the insecticide.